COURSE of the MONTH

Exchange Hub / Dumpster

If I understand, Exchange 2010 uses the log shipping between 2 database to keep them synchronized.
The Hub-T server has a role as "Dumpster".
Now, let say the Mailbox server1 has the active copy of the DB and when in the process of synching with MB2 , it has failed and the MB2 became the Active. how does the MB2 get the missing emails from MB1 seeing that the synching was not complete.?

Does your mouse not work? The article gives a FULL explination of how exchange 2010 handles continuos replication. You should be reading the whole article if you wish to "Understand" this in full. I pointed out the section of the article to pay extra attention to, not the ONLY bit to read.

You are talking about what is called "Shadow redundancy" the idea is that the email is never deleted unless you get the confirmation it was sent by the next hop.

for example

1. MBX1 delivers email to Hub1 and it keeps a copy from it
2. MBX1 checks periodically with HUB1 till it gets the acknowledge from HUB1 that he delivered the email to the next hop (no matter who is the next hop)
3. MBX1 deletes the email

the email is now in HUB1 that will follow the same logic

1. HUB1 delivers the email to MBX2
2. HUB2 will check with MBX2 that it was delivered to the mailbox
3. When he gets the acknowledge it will delete it from HUB2

assuming in the steps 2 above the acknowledge was not received the server (mbx1 or hub1 depending on which scenario) will try to resend the email through another route.

This could lead to duplicate emails in the case the email was delivered and the server failed before sending the acknowledge however no emails get lost

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jskfanAuthor Commented: 2011-09-15

I found this article:

The function of the Transport Dumpster has changed in Exchange 2010. When using DAGs the transport dumpster now receives feedback from the replication pipeline to determine which messages have been delivered and replicated. As a message goes through Hub Transport Servers on its way to a replicated mailbox database in a DAG, a copy is kept in the transport queue until the replication pipeline has notified the Hub Transport server that the transaction logs representing the message have been successfully replicated to and inspected by all copies of the mailbox database. Once the logs have been replicated to and inspected by all database copies, they are truncated from the transport dumpster. This keeps the transport dumpster queue leaner by maintaining only copies of messages whose transactions logs have not yet been replicated